1. Field of the Invention
The present invention relates to a wireless communication device for transmitting and receiving data, for example, by radiowaves, and to a printing system employing such a device.
2. Description of the Related Art
In a network of conventional wireless communication devices, the transmission power of each device is set strong enough to be received by the farthest device. A network of wireless communication devices is illustrated in FIG. 5, in which a symbol "0" indicates a wireless communication device. The transmission power of a device 10 is set so that a device 1 farthest from the device 10 can receive the data sent by the device 10. The transmission power of a device 4 can be set lower than that of the device 10, since the device 4 is located substantially at the center of the network so that the distance from the device 4 to the farthest device therefrom is shorter than the distance from the device 10 to the device 1.
Thus, in a network, different devices may have different transmission power levels, according to their locations in the network.
Such a network or device, however, has problems as described below.
Devices located in the peripheral area of the network, such as the device 10 in FIG. 5, use significantly more power than devices located in the central area of the network, such as the device 4. For example, the device 10 always uses the same high power to transmit data to any device, whether to the farthest device 1 or to the neighboring devices 4, 7 and 8. Also, the high power radiowaves sent out by the device 10 naturally reach the area outside the network (e.g., the area below the unit 10 in FIG. 5) as well, so that communication between the devices in the network can be received by a device outside the network. This becomes a significant problem when confidential data is communicated in the network. As a result, security protection becomes difficult.